Illustrations of the thermodynamics of bubble nucleation where a fluctuation can grow from a critical radius r_crit onwards when the thermodynamic driving force for the phase separation ΔG_V overcomes the energy penalty for forming an interface [61, 62] (A). As a consequence, the phase equilibrium defined by the respective equation of state represents only the equilibrium co-existence of pre-existing phases, while phase separation occurs when a single phase below that coexistence condition becomes unstable against nucleation or fluctuations by e.g. spinodal decomposition [66] (B).